U.S. patent number 8,283,477 [Application Number 12/999,420] was granted by the patent office on 2012-10-09 for method for preparing n-substituted maleimides.
This patent grant is currently assigned to Korea Kumho Petrochemical Co., Ltd.. Invention is credited to Jin-Eok Kim, Seung-il Kim, Han-Jin Kwag.
United States Patent |
8,283,477 |
Kim , et al. |
October 9, 2012 |
Method for preparing N-substituted maleimides
Abstract
The present invention relates to a method of preparing
N-substituted maleimide in high purity and high yield, wherein,
unlike a conventional method of preparing N-substituted maleimide
after preparing N-substituted maleamic acid, an organic solvent, an
acid catalyst, a dehydration co-catalyst and a stabilizer are added
into a reactor without separately preparing N-substituted maleamic
acid, and then a primary amine is added into the reactor to form an
amine salt, maleic anhydride is added into the reactor, and the
resulting mixture is subjected to a dehydration-cyclization
reaction, wherein water produced during the reaction is
azeotropically distilled with the organic solvent so as to
effectively suppress formation of a maleimide polymer.
Particularly, the invention simplifies the process, has high yield,
minimizes side reactions, eliminates the introduction of expensive
raw materials and the complicated treatment of the reaction
solution and significantly shortens the time over which the raw
materials and maleic anhydride are added.
Inventors: |
Kim; Jin-Eok (Daejeon,
KR), Kim; Seung-il (Daejeon, KR), Kwag;
Han-Jin (Daejeon, KR) |
Assignee: |
Korea Kumho Petrochemical Co.,
Ltd. (Seoul, KR)
|
Family
ID: |
41669425 |
Appl.
No.: |
12/999,420 |
Filed: |
June 24, 2009 |
PCT
Filed: |
June 24, 2009 |
PCT No.: |
PCT/KR2009/003405 |
371(c)(1),(2),(4) Date: |
December 16, 2010 |
PCT
Pub. No.: |
WO2010/018926 |
PCT
Pub. Date: |
February 18, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110124882 A1 |
May 26, 2011 |
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Foreign Application Priority Data
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Aug 11, 2008 [KR] |
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10-2008-0078595 |
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Current U.S.
Class: |
548/451 |
Current CPC
Class: |
C07D
207/448 (20130101) |
Current International
Class: |
A61K
31/4015 (20060101); A61K 31/402 (20060101); C07D
207/40 (20060101) |
Field of
Search: |
;548/451 ;514/425 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 257 831 |
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Mar 1988 |
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EP |
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0 334 497 |
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Sep 1989 |
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EP |
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0334497 |
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Sep 1989 |
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EP |
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52-13869 |
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Feb 1977 |
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JP |
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53-068770 |
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Jun 1978 |
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JP |
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57-042043 |
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Mar 1982 |
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JP |
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Other References
Coleman, Lester E. et al.: "Reaction of Primary Aliphatic Amines
with Maleic Anhydride", Notes, Jan. 1959, pp. 135-136. cited by
other.
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Primary Examiner: Saeed; Kamal
Assistant Examiner: Coppins; Janet L
Attorney, Agent or Firm: Frommer Lawrence & Haug LLP
Santucci; Ronald R
Claims
The invention claimed is:
1. A method of preparing N-substituted maleimide in high purity and
high yield, the method comprising: introducing an organic solvent;
an acid catalyst; polyalkylene glycol having a molecular weight of
1.000-10.000 as a catalyst binder; a dehydration co-catalyst
selected from the group consisting of oxides, acetates, maleates,
succinates, and chlorides with at least one metal selected from the
group consisting a zinc (Zn), chromium (Cr), palladium (Pd), cobalt
(Co), nickel (Ni), iron (Fe), and aluminum (Al); and a stabilizer
into a reactor; introducing a primary amine into the reactor to
form an amine salt; introducing maleic anhydride into the reactor;
and subjecting the resulting mixture to a dehydration-cyclization
reaction, wherein water produced during the reaction is
azeotropically distilled.
2. The method of claim 1; wherein the organic solvent is used in an
amount equal to 1-20 times the weight of the primary amine.
3. The method of claim 2; wherein the organic solvent is one or
more selected from the group consisting of benzene, toluene,
xylene, ethylbenzene, cumene, chlorobenzene, isopropylbenzene,
mesitylene, t-butylbenzene, trimethyl hexane, and octane.
4. The method of claim 1; wherein the acid catalyst is one or more
selected from the group consisting of anhydrous sulfonic acid,
p-toluene sulfonic acid, orthophosphoric acid, metaphosphoric acid,
pyrophosphoric acid, benzenesulfonic acid and trichloroacetic
acid.
5. The method of claim 1; wherein the acid catalyst is used in an
amount of 10-200 molar parts based on 100 molar parts of the
primary amine.
6. The method of claim 1; wherein the acid catalyst is added in a
state supported on a carrier.
7. The method of claim 6; wherein the carrier is used in an amount
equal to 0.2-2 times the weight of the acid catalyst.
8. The method of claim 6; wherein the carrier is one or more
selected from the group consisting of activated carbon, silica,
silica-alumina, titanium dioxide and zirconium oxide, natural
mineral materials, clay, talc, diatomaceous earth, bentonite and
montmorillonite.
9. The method of claim 1; wherein the polyalkylene glycol is
polyethylene glycol or polypropylene glycol.
10. The method of claim 1; wherein the catalyst binder is used in
an amount equal to 0.2-2 times the weight of the acid catalyst.
11. The method of claim 1; wherein the dehydration co-catalyst is
used in an amount of 0.005-5 molar parts based on 100 molar parts
of the primary amine.
12. The method of claim 1 wherein the stabilizer is at least one
selected from the group consisting of methoxy benzoquinone,
p-methoxyphenol, phenothiazine, hydroquinone, alkylated diphenyl
amines, methylene blue, tert-butyl catechol, tert-butyl
hydroquinone, zinc dimethyldithiocarbamate, copper
dimethyldithiocarbamate, alkylphenols, and alkylbisphenols.
13. The method of claim 1; wherein the stabilizer is used in an
amount of 0.005-5 molar parts based on 100 molar parts of the
primary amine.
14. The method of claim 1; wherein the primary amine is at least
one selected from the group consisting of methylamine, ethylamine,
n-propylamine, i-propylaminc, s-propylamine, n-butylamine,
s-butylamine, i-butylamine, t-butylamine, n-hexylamine,
n-dodecylamine, allylamine, benzylamine, cyclohexylamine, aniline,
ethylaniline, toluidine, hydroxyaniline, nitroaniline and
ethylenediamine.
15. The method of claim 1; wherein tert-amine is additionally added
before the primary amine is added.
16. The method of claim 15; wherein the tert-amine is added in an
amount of 0.05-50 molar parts based on 100 parts of the primary
amine.
17. The method of claim 15; wherein the tert-amine is at least one
selected from the group consisting of trimethylamine,
triethylamine, tripropylamine, tributylamine, tripentylamine,
trioctylamine and tribenzylamine.
18. The method of claim 1; wherein the maleic anhydride is added in
an amount of 100-150 molar parts based on 100 molar parts of the
primary amine.
19. The method of claim 1; wherein the maleic anhydride is
additionally added as required during the reaction.
20. The method of claim 1; wherein the reaction is carried out at a
temperature or 50-200.degree. C.
Description
This application is a 371 of PCT/KR2009/003405 filed on Jun. 24,
2009 published on Feb. 18, 2010 under publication number WO
2010/018926 A which claims priority benefits to Korean Patent
Application Number 10-2008-0078595 filed Aug. 11, 2008, the
disclosure of which is incorporated herein by reference.
TECHNICAL FIELD
The present invention relates to a method for preparing
N-substituted maleimide.
BACKGROUND ART
N-substituted maleimides are useful as starting materials or
intermediates for the preparation of pharmaceuticals, agricultural
chemicals, dyes, polymer compounds and the like. Recently, they
have been used in large amounts to improve the heat resistance of
styrene resins and are also widely used in copolymers for resin
modification or polymer compounding.
There have been known a few methods for preparing N-substituted
maleimides. A conventional preparation method comprises allowing
maleic anhydride to react with an amine to obtain N-substituted
maleamic acid which is then subjected to dehydrocyclization
(imidization). As one example, there is a method in which
N-substituted maleamic acid obtained by heating maleic anhydride
and amine at 180.degree. C. is subjected to dehydrocyclization [L.
E. Coleman et al., J. Org, Chem., 24, 135.about.136 (1959)].
However, this method is not economical, because the desired
N-substituted maleimide is obtained in a yield of only about
15-50%.
Methods of preparing N-substituted maleimide in a relatively yield
include methods in which a dehydrating agent or a dehydration
catalyst is used for dehydrocyclization of N-substituted maleamic
acid.
One example of the method that uses the dehydrating agent is
disclosed in U.S. Pat. No. 2,444,536 in which N-substituted
maleamic acid is dehydrocyclized using a dehydrating agent such as
acetic anhydride in the presence of a sodium acetate catalyst. This
method has a relatively high reaction yield, but it incurs a high
production cost, because it uses a large amount of the dehydrating
agent and carries out a complicated process of separating the
product after the reaction. Thus, it is not an economical
mass-production method.
Methods that are considered industrially advantageous include
methods of dehydrocyclizing N-substituted maleamic acid under mild
conditions using an effective dehydrating agent in place of the
dehydrating agent. These methods do not use expensive
sub-materials, and thus can be economically advantageous. U.S. Pat.
No. 3,431,276 discloses a method of preparing N-substituted
maleimides by heating and dehydrocyclizing N-substituted maleamic
acid using an acid catalyst, such as sulfur trioxide, sulfuric acid
or orthophosphoric acid, in a solvent having a suitable boiling
point, without using a chemical dehydrating agent, and removing
Thus produced water from the reaction system by azeotropic
distillation. This method is advantageous in that an expensive
dehydrating agent is not used and N-substituted maleimide can be
easily separated, but the yield from the reaction is low and is
likely to involve side reactions. In an attempt to improve this
reaction yield, Japanese Patent Laid-Open Publication Nos.
53-68,770 and 57-42,043 disclose a method of preparing
N-substituted maleimide by producing N-substituted maleamic acid,
increasing the solubility of the N-substituted maleamic acid using
an aprotic polar solvent such as dimethylformamide or
dimethylsulfoxide and then dehydrocyclizing the N-substituted
maleamic acid in the presence of an acid catalyst. The use of this
aprotic polar solvent greatly increases the yield of N-substituted
maleimide, but this solvent is expensive and highly toxic, and
increases the production cost, because it is used in large amount.
Also, this aprotic polar solvent can be deteriorated by the acid
catalyst during the reaction, and thus needs to be used in a large
amount. In addition, because this solvent has a high boiling point,
much energy is required to separate the solvent from N-substituted
male imide.
U.S. Pat. Nos. 4,623,734, 4,780,546 and 4,786,738 disclose methods
comprising allowing maleic anhydride to react with amine in a
non-polar organic solvent so as to produce N-substituted maleamic
acid, and then dehydrocyclizing the N-substituted maleamic acid by
azeotropic distillation in the presence of an acid stabilizer and
other stabilizers. However, in the above methods, highly purified
N-substituted maleimide cannot be prepared, and it is very
difficult to separate the catalyst from the reaction solution after
completion of the reaction due to the byproducts produced during
the reaction. Even when the separation of the catalyst is achieved,
the activity of the catalyst is rapidly reduced such that it cannot
be effectively recycled. For the above reason, this method is not
advantageous from an economical point of view.
U.S. Pat. No. 4,851,547 discloses supporting a catalyst on a solid
carrier in order to facilitate the separation of the catalyst. This
method appears to be suitable from an economical aspect, but
reactors are required to be used separately, because maleic
anhydride and amine are first allowed to react with each other to
prepare N-substituted maleamic acid, and then an amine salt that
was separately prepared is treated with acid and applied as a
catalyst to the prepared N-substituted maleamic acid. Also, there
is a problem that the N-substituted maleamic acid or the amine salt
should be transferred in a slurry state. Furthermore, there is a
problem in that a large amount of 2-amino-N-substituted succinimide
is produced as a byproduct due to the use of an excessive amount of
the amine during the reaction. In addition, because the amine that
acts as a catalyst actually participates in the reaction, it is not
suitable for the preparation of high-purity N-substituted
maleimide.
U.S. Pat. No. 4,980,483 uses a two-stage reaction on the basis of
the phenomenon in which the major byproduct 2-amino-N-substituted
succinimide reacts with maleic anhydride so as to be selectively
converted to N-substituted maleimide. According to the disclosure
therein, in the former stage, a reaction is carried out using amine
in an excess amount such that 2-amino-N-substituted succinimide can
be produced, and in the latter stage, an excess amount of maleic
anhydride is added, whereby N-substituted maleimide can be obtained
in high yield and purity. However, a large amount of
2-amino-N-substituted succinimide is converted to N-substituted
maleimide only under the condition that an excess amount of maleic
anhydride is present, and non-converted 2-amino-N-substituted
succinimide is an impurity present in the final product. For this
reason, the above method is not suitable in a field requiring a
high degree of purification. Also, 2-amino-N-substituted
succinimide contained in the polymer compound can carbonize the
surface of the polymer compound or make the surface of a final
product irregular, and thus it should be removed.
U.S. Pat. No. 5,973,166 discloses a method in which a large amount
of amine salt is used in place of an aprotic polar solvent to
increase the solubility of reactants, intermediates and products in
the prior-art maleimide preparation methods. However, this method
has problems occurring when N-substituted maleamic acid is prepared
first, like other preparation methods. Also, it has a relatively
low yield and has a problem in that the purification process using
recrystallization is complex. In addition, it is not advantageous
from an economical viewpoint, because the expensive amine salt is
used in large amount.
DISCLOSURE
Technical Problem
Accordingly, the present inventors have studied on a preparation
method for preparing N-substituted maleimide, which uses a simple
reaction, has a high yield and minimizes side reactions, compared
to conventional methods. As a result, the present inventors have
developed a method of preparing N-substituted maleimide, wherein,
unlike a conventional method of preparing N-substituted maleamic
acid in advance, an acid catalyst, a dehydration co-catalyst and a
stabilizer are added to an organic solvent, primary amine is added
thereto to form an amine salt, and then maleic anhydride is added
thereto, and the resulting mixture is subjected to a
dehydration-cyclization reaction, whereby the introduction of
expensive raw material and the complicated treatment of the
reaction solution, which are the problems of the conventional
method, are eliminated, an aprotic polar solvent of high-boiling
point is not used, the purification process is simple, and the
separation and recycling of the catalyst is easy. By developing
this preparation method, the present invention has been
completed.
Technical Solution
The present invention provides a method of preparing N-substituted
maleimide in high purity and high yield, the method sequentially
comprising: introducing an organic solvent, an acid catalyst, a
dehydration co-catalyst and a stabilizer into a reactor;
introducing a primary amine into the reactor to form an amine salt;
introducing maleic anhydride into the reactor; and subjecting the
resulting mixture to a dehydration-cyclization reaction, wherein
water produced during the reaction is azeotropically distilled.
Advantageous Effects
It was found that the inventive method of preparing N-substituted
maleimide using an amine salt as both a reactant and a catalyst
could give a higher yield and result in higher purity than a
conventional method of preparing N-substituted maleimide after
preparing N-substituted maleamic acid. Also, it could be seen that
the use of a suitable amount of tert-amine could result in a higher
yield and purity. In addition, adding maleic anhydride in a
suitable manner resulted in a higher yield.
BEST MODE
Hereinafter, the present invention will be described in further
detail.
The present invention relates to a method of preparing
N-substituted maleimide in high purity and high yield, wherein,
unlike a conventional method of preparing N-substituted maleimide
after preparing N-substituted maleamic acid, an organic solvent, an
acid catalyst, a dehydration co-catalyst and a stabilizer are added
into a reactor without separately preparing N-substituted maleamic
acid, and then primary amine is added into the reactor to form an
amine salt, maleic anhydride is added into the reactor, and the
resulting mixture is subjected to a dehydration-cyclization
reaction, wherein water produced during the reaction is
azeotropically distilled with the organic solvent so as to
effectively suppress formation of a maleimide polymer.
First, components that are used to prepare N-substituted maleimide
according to the present invention will be described.
Examples of the primary amine that is particularly useful as a raw
material for maleimide which is used in the present invention
include methylamine, ethylamine, n-propylamine, i-propylamine,
s-propylamine, n-butylamine, s-butylamine, i-butylamine,
t-butylamine, n-hexylamine, n-dodecylamine, allylamine,
benzylamine, cyclohexylamine, aniline, ethylaniline, toluidine,
hydroxyaniline, nitroaniline and ethylenediamine.
The organic solvent that is used in the present invention must be
insoluble in or immiscible with water, must be inactive in the
reaction and must not participate in the reaction, such that water
produced by the dehydrocyclization of N-substituted maleamic acid
can be released from the reaction system by azeotropic
distillation. Also, the boiling point thereof is preferably at
least 50.degree. C. for the reaction to proceed properly, but less
than 170.degree. C. for the stability of produced N-substituted
maleamide. Examples of organic solvent suitable for use in the
present invention include benzene, toluene, xylene, ethylbenzene,
cumene, chlorobenzene, isopropylbenzene, mesitylene,
t-butylbenzene, trimethyl hexane octane, and the like. So that the
reaction proceeds properly and from an economical viewpoint, the
amount of the organic solvent that is used in the reaction is
preferably about 1-20 times the weight of primary amine used as a
raw material, and more preferably about 2-10 times the weight of
primary amine.
Also, the organic solvent should be selected in consideration of
environmental factors, solubility for the raw material and the
product, cost and handling easiness, and the selected solvent must
be easily removed and suitably recycled after the reaction. Also,
the organic solvents may be used alone or in combination, and the
mixing ratio of the solvents can be determined so as to achieve the
above object.
Preferred examples of an acid catalyst that may be used in the
present invention include inorganic or organic monobasic or
polybasic acids, such as anhydrous sulfuric acid, p-toluenesulfonic
acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric
acid, benzenesulfonic acid and trichloroacetic acid. This catalyst
is used in an amount of about 10-200 molar parts, and preferably
20-100 molar parts, based on 100 molar parts of primary amine which
is used in the reaction. If the catalyst is used in an amount of
less than 10 molar parts, the reaction will not properly occur, and
if it is more than 200 molar parts, it will reduce yield and result
in side reactions.
Meanwhile, the catalyst may be supported on a carrier. Examples of
a carrier that can support the catalyst include synthetic mineral
materials, such as activated carbon, silica, silica-alumina,
titanium dioxide and zirconium oxide, and natural mineral materials
such as clay, talc, diatomaceous earth, bentonite and
montmorillonite. Such an inorganic carrier is used in the form of
powder or in the form of granules obtained by pelletizing and
classifying the relevant substance. The catalysis is obtained with
particularly desirable results when the carrier is made of such a
porous substance as diatomaceous earth, silica gel or activated
carbon. The amount of carrier applied is 0.2-4 times the weight of
catalyst added, and preferably 0.5-2 times the weight of catalyst
added.
When a catalyst binder is used together with the catalyst, it can
increase the activity of the catalyst and makes it possible to
recycle the catalyst. The catalyst binder must have low solubility
in an organic solvent, must be physically or chemically bonded with
the catalyst such that it is not separated from the catalyst, and
must be easily mixed with reactants during the reaction. As the
catalyst binder, polyalkylene glycol, polyvinyl alcohol or the like
which have a molecule weight of 1000-10000 may be used. Preferably,
polyethylene glycol (PEG) or polypropylene glycol (PPG) is used.
The amount of catalyst binder used is 0.2-4 times the weight of
catalyst added, and preferably 0.5-2 times the weight of the
catalyst added.
The above reaction produces even better results when it is allowed
to proceed in the presence of a metal-containing compound, as a
dehydration co-catalyst, and a stabilizer. The metal-containing
compound may be selected from the group consisting of oxides,
acetates, maleates, succinates, and chlorides with at least one
metal selected from the group consisting of zinc (Zn), chromium
(Cr), palladium (Pd), cobalt (Co), nickel (Ni), iron (Fe) and
aluminum (Al). Of these, zinc acetate proved to be particularly
effective. The metal-containing compound is used in an amount of
0.005-5 molar parts, and preferably 0.01-4 molar parts, based on
100 molar parts of primary amine. If the dehydration co-catalyst is
used in an amount of less than 0.005 molar parts, the reaction time
will be increased, and if it is used in an amount of 5 molar parts,
it will result in side reactions and reduce the activity of the
catalyst.
Examples of the effective stabilizer in the present invention
include methoxy benzoquinone, 2,6-t-butyl-4-methylphenol (BHT),
p-methoxyphenol, phenothiazine, hydroquinone, alkylated diphenyl
amines, methylene blue, tert-butyl catechol, tert-butyl
hydroquinone, zinc dimethyldithiocarbamate, copper
dibutyldithiocarbamate, alkylphenols, and alkylbisphenols.
Concerning the amount of the stabilizer to be added, the addition
of the stabilizer in a minute amount is not sufficiently effective
and the addition thereof in an unduly large amount is undesirable
because it affects the production of a final product, particularly
a polymer compound. The stabilizer is used in an amount of 0.005-5
molar parts, and preferably 0.05-3 molar parts, based on 100 molar
parts of primary amine. If the stabilizer is used in an amount of
less than 0.005 molar parts, it can cause the formation of a
maleimide polymer, and if it is used in an amount of more than 5
molar parts, it will excessively affect the final product such that
it can act as a catalytic poison to the polymerization.
As described above, the present invention is characterized in that
an amine salt is formed first by introducing an organic solvent, an
acid catalyst, a dehydration co-catalyst and a stabilizer into a
reactor and then introducing primary amine into the reactor.
Particularly, when tert-amine acts as a co-catalyst before
introducing the primary amine, the reaction conditions can be
controlled to a mild condition. Namely, tert-amine may be used as a
co-catalyst for a dehydration-cyclization reaction, and suitable
tert-amine can control the acidity of the reaction system to
control excessive reactions and can effectively suppress the
production of a polymer from being formed by thus produced
N-substituted maleimide. Examples of tert-amine that may be used in
the present invention include trimethylamine, triethylamine,
tripropylamine, tributylamine, tripentylamine, trioctylamine and
tribenzylamine. The tert-amine is used in an amount of
0.05-50(0.01-50) molar parts, and preferably 0.01-20(0.05-20) molar
parts, based on 100 molar parts of the primary amine. If the
tert-amine is used in an amount of less than 0.05 (0.01) molar
parts, it will not effectively suppress side reactions, and if it
is used in an amount of more than 50 molar parts, it will reduce
yield and make a washing process difficult.
In the present invention, maleic anhydride is added after the
formation of the amine salt and is preferably used in an amount of
100-150 molar parts based on 100 molar parts of the primary amine.
In addition to adding the maleic anhydride after formation of the
amine salt as described above, additional maleic anhydride may also
be added after the middle stage of the reaction in order to achieve
a higher purity and yield. The amount of maleic anhydride that is
additionally added is preferably 0.1-30 mole % based on the total
amount of maleic anhydride used.
In the preparation method of the present invention, the reaction
temperature is generally 50.about.200.degree. C., and preferably
70.about.160.degree. C. The pressure in the present invention is
not specifically limited, but may be selected from reduced
pressure, atmospheric pressure and elevated pressure. The reaction
time varies depending on the type of solvent, the amount of raw
material added and the reaction temperature, but is generally about
1-16 hours, and preferably 1-10 hours.
Following the reaction in the present invention can prepare
N-substituted maleamide in high purity and high yield by
introducing an organic solvent into a reactor, introducing an acid
catalyst and, if necessary, a catalyst carrier, introducing a
dehydration co-catalyst and a stabilizer, introducing tert-amine
together with a primary amine for producing N-substituted maleimide
so as to be partially or completely aminated, introducing maleic
anhydride at one time or in portions, subjecting the resulting
mixture to dehydration-cyclization, and removing thus produced
water together with the organic solvent from the reaction system.
The solvent and catalyst used in the reaction can be easily
separated such that they may be used in another reaction without
modification.
The present invention omits a separate process of making
N-substituted maleamic acid, unlike conventional methods. Thus,
only one reactor may be used, and a process of transferring
N-substituted maleamic acid in a slurry state can be omitted,
making the preparation process simple. Also, inconvenience
associated with the transfer of N-substituted maleamic acid
disappears, and the reaction can be completed in one reactor
without needing to use a separate reactor. Moreover, it could be
seen that the use of the method according to the present invention
could provide a higher yield and purity than the method of
preparing N-substituted maleimide after preparing N-substituted
maleamic acid. More details will be described in the Examples
below.
Unlike conventional methods in which the same kind of amine salt as
an amine participating in the reaction is separately formed so as
to be used as a catalyst, the present invention forms an amine salt
from an amine participating in the reaction, thereby preventing an
excessive amount of amine from being used in the reaction system.
Thus, the major product 2-amino-N-substituted succinimide is not
formed and is used in an equivalent amount, and thus the present
invention is advantageous from an economical viewpoint. Also, in
conventional methods, amine is added over a time ranging from 30
minutes to 1 hour or longer in order to avoid the formation of side
reactions during the formation of N-substituted maleimide, whereas,
in the present invention, an amine is added within 10 minutes, and
thus the reaction time is shortened.
Unlike conventional methods in which maleic anhydride is added
first into the organic solvent such that it is easily modified into
maleic acid by water in the reaction system, the present invention
can prevent maleic anhydride from being modified, because maleic
anhydride is added into the prepared reaction system within a short
time. Thus, the production of maleic acid from maleic anhydride or
the production of fumaric acid from maleic anhydride by a
rearrangement reaction can be prevented, thus providing a higher
yield and purity than do the conventional methods.
MODE FOR INVENTION
Hereinafter, the present invention will be described in further
detail with reference to examples, but the scope of the present
invention is not limited thereto.
Example 1
Into a 300-ml reactor equipped with a thermometer, a cooler having
a water separator attached thereto, and a stirrer, 88 g of a 1:1
mixed solvent of xylene and toluene was added. Then, 8 g (69.4
mmol) of 85% o-phosphoric acid was added and refluxed while
stirring to remove water.
Then, 1.2 g (6.54 mmol) of zinc acetate and 1 g (4.54 mmol) of BHT
were added. While stirring the reaction mixture, 20 g (214.8 mmol)
of aniline was added for 5 minutes to form an amine salt, and 22 g
(224.3 mol) of maleic anhydride was added into the reactor for 5
minutes. Then, the temperature of the reactor was increased to
125.degree. C., and the content of the reactor was refluxed. Thus
produced water was azeotropically distilled together with the mixed
solvent to be removed from the reactor through the water separator.
The reaction was performed at the temperature for 3 hours, and then
1.4 g of maleic anhydride was additionally added and allowed to
react for 2 hours. The reaction was stopped, the content of the
reactor was cooled to 30.degree. C., and the catalyst layer was
removed by layer separation. The xylene and toluene solution layers
were transferred into a separate neutralization tank, and 50 g of
5% sodium carbonate aqueous solution was added thereto. The
solution was stirred for 20 minutes and then allowed to stand for
20 minutes. The solution was separated clearly into an organic
layer and an aqueous layer which was then separated and removed. 50
g of water was added to the organic layer, and the solution was
stirred for 20 minutes and allowed to stand for 20 minutes. Thus
formed aqueous layer was separated and removed. Thus separated
organic layer was then transferred into a concentration tank, and
then distilled under a reduced pressure of 20.about.130 mmHg at
50.about.100.degree. C. to remove xylene and toluene. As a result,
in the concentration tank, 27.0 g of a light-yellow solid material
was obtained. The solid material was analyzed by liquid
chromatography. The result showed 98% purity of N-phenylmaleimide,
and 87% yield of N-phenylmaleimide based on aniline. As byproducts,
0.2% 2-amino-N-substituted succinimide and 1.2% N-phenylmaleimide
dimer.
Example 2
Into a 100-L reactor equipped with a thermometer, a cooler having a
water separator attached thereto, and a stirrer, 40 kg of xylene
was added. Then, 2 kg of silica gel as a carrier was added,
followed by 2 kg (17.3 mol) of o-phosphoric acid was added.
Then, 30 g (0.19 mol) of zinc acetate and 30 g (0.14 mol) of
2,4-dimethyl-6-t-butylphenol were added. 100 g (0.98 mol) of
triethylamine was added to neutralize the solution, and then 4 kg
(43.0 mol) of aniline was added into the reactor for 5 minutes to
form an amine salt. Then, 4.6 kg (47.3 mol) of maleic anhydride was
added into the reactor for 5 minutes. Then, keeping the temperature
of the reactor at 140.degree. C. while stirring, thus produced
water was azeotropically distilled together with the xylene to be
removed from the reactor through the water separator. The reaction
was performed at the temperature for 6 hours. The reaction was
stopped, the content of the reactor was cooled to 30.degree. C.,
and the catalyst layer was removed by layer separation. The xylene
solution layer was transferred into a separate neutralization tank,
and 500 g of 5% sodium carbonate aqueous solution was added
thereto. The solution was stirred for 20 minutes and then allowed
to stand for 20 minutes. The solution was separated clearly into an
organic layer and an aqueous layer which was then separated and
removed. Then, 500 g of water was added to the organic layer, and
the solution was stirred for 20 minutes and allowed to stand for 20
minutes. Thus formed aqueous layer was separated and removed. Thus
separated organic layer was then transferred into a concentration
tank, and distilled under a reduced pressure of 20.about.130 mmHg
at 50.about.100.degree. C. to remove xylene. After removal of the
solvent, 7.2 kg of a light-yellow solid material was obtained in
the concentration tank. The solid material was analyzed by liquid
chromatography. The result showed 98% purity of N-phenylmaleimide,
and 97% yield of N-phenylmaleimide based on aniline.
Example 3
Into a 100-L reactor equipped with a thermometer, a cooler having a
water separator attached thereto, and a stirrer, 40 kg of xylene
was added. Then, 2 kg of silica gel as a carrier was added,
followed by 2 kg (17.3 mol) of o-phosphoric acid. Then, 30 g (0.19
mol) of zinc acetate and 30 g (0.14 mol) of
2,4-dimethyl-6-t-butylphenol were added. 200 g (1.98 mol) of
triethylamine was added to neutralize the solution, and then 4 kg
(43.0 mol) of aniline was added into the reactor for 5 minutes to
form an amine salt. Then, 4.6 kg (47.3 mol) of maleic anhydride was
added into the reactor for 5 minutes. Then, keeping the temperature
of the reactor at 140.degree. C. while stirring, thus produced
water was azeotropically distilled together with the xylene to be
removed from the reactor through the water separator. The reaction
was performed at the temperature for 3 hours, and then 200 g of
maleic anhydride was additionally added and allowed to react for 3
hours. Then, the reaction was stopped, the content of the reactor
was cooled to 30.degree. C., and the catalyst layer was removed by
layer separation. The xylene solution layer was transferred into a
separate neutralization tank, and 500 g of 5% sodium carbonate
aqueous solution was added thereto. The solution was stirred for 20
minutes and then allowed to stand for 20 minutes. The solution was
separated clearly into an organic layer and an aqueous layer which
was then separated and removed. Then, 500 g of water was added to
the organic layer, and the solution was stirred for 20 minutes and
allowed to stand for 20 minutes. Thus formed aqueous layer was
separated and removed. Thus separated organic layer was then
transferred into a concentration tank, and distilled under a
reduced pressure of 20.about.130 mmHg at 50.about.100.degree. C. to
remove xylene. After removal of the solvent, 7.3 kg of a
light-yellow solid material was obtained in the concentration tank.
The solid material was analyzed by liquid chromatography. The
result showed the 99% purity of N-phenylmaleimide and 97% yield of
N-phenylmaleimide based on aniline.
Example 4
Experiment was conducted in the same manner as Example 3, except
that 300 g (2.94 mol) of triethylamine was added (addition time of
primary amine: 5 min; addition time of maleic anhydride: 5 min). As
a result, 7.3 kg of a light-yellow solid material was obtained in
the concentration tank. The solid material was analyzed by liquid
chromatography. The result showed 99% purity of N-phenylmaleimide
and 98% yield of N-phenylmaleimide based on aniline.
Example 5
Experiment was conducted in the same manner as Example 2, except
that 3 kg (26.0 mol) of o-phosphoric acid as a catalyst was added
(addition time of primary amine: 5 min; addition time of maleic
anhydride: 5 min). As a result, 7.1 kg of a brown-yellow solid
material was obtained in the concentration tank. The solid material
was analyzed by liquid chromatography. The result showed 97% purity
of N-phenylmaleimide and 96% yield of N-phenylmaleimide based on
aniline.
Example 6
Experiment was conducted in the same manner as Example 2, except
that 1 kg (8.7 mol) of o-phosphoric acid as a catalyst was added
(addition time of primary amine: 5 min; addition time of maleic
anhydride: 5 min). As a result, 7.1 kg of a brown-yellow solid
material was obtained in the concentration tank. The solid material
was analyzed by liquid chromatography. The result showed 97% purity
of N-phenylmaleimide and 96% yield of N-phenylmaleimide based on
aniline.
Example 7
Experiment was conducted in the same manner as Example 2, except
that 30 kg of xylene as a solvent was added (addition time of
primary amine: 5 min; addition time of maleic anhydride: 5 min). As
a result, 7.1 kg of a brown-yellow solid material was obtained in
the concentration tank. The solid material was analyzed by liquid
chromatography. The result showed 97% purity of N-phenylmaleimide
and 96% yield of N-phenylmaleimide based on aniline.
Example 8
Experiment was conducted in the same manner as Example 3, except
that 20 g (0.12 mol) of 6-butylcatechole as a stabilizer was added
in place of 2,4-dimethyl-6-t-butylphenol (addition time of primary
amine: 5 min; addition time of maleic anhydride: 5 min). As a
result, 7.2 kg of a brown-yellow solid material was obtained in the
concentration tank. The solid material was analyzed by liquid
chromatography. The result showed 97% purity of N-phenylmaleimide
and 97% yield of N-phenylmaleimide based on aniline.
Example 9
Experiment was conducted in the same manner as Example 3, except
that 400 g of maleic anhydride was additionally added after 3 hours
of the reaction (addition time of primary amine: 5 min; addition
time of maleic anhydride: 5 min). As a result, 7.1 kg of a
brown-yellow solid material was obtained in the concentration tank.
The solid material was analyzed by liquid chromatography. The
result showed 99% purity of N-phenylmaleimide and 98% yield of
N-phenylmaleimide based on aniline.
Example 10
Experiment was conducted in the same manner as Example 3, except
that 800 g of maleic anhydride was additionally added after 3 hours
of the reaction (addition time of primary amine: 5 min; addition
time of maleic anhydride: 5 min). As a result, 7.1 kg of a
brown-yellow solid material was obtained in the concentration tank.
The solid material was analyzed by liquid chromatography. The
result showed 97% purity of N-phenylmaleimide and 97% yield of
N-phenylmaleimide based on aniline.
Example 11
Into a 100-L reactor equipped with a thermometer, a cooler having a
water separator attached thereto, and a stirrer, 40 kg of xylene
was added. Then, 2 kg of silica gel as a carrier was added, after
which 2 kg (17.3 mol) of o-phosphoric acid was added. Then, 30 g
(0.19 mol) of zinc acetate and 30 g (0.14 mol) of
2,4-dimethyl-6-t-butylphenol were added. 200 g (1.96 mol) of
triethylamine was added to neutralize the solution, and then 4 kg
(43.0 mol) of cyclohexylamine was added into the reactor for 5
minutes to form an amine salt.
Then, 4.4 kg of maleic anhydride was added into the reactor for 5
minutes. Then, while keeping the temperature of the reactor at
140.degree. C., thus produced water was azeotropically distilled
together with the xylene to be removed from the reactor through the
water separator. The reaction was performed at the temperature for
3 hours, and then 200 g of maleic anhydride was additionally added
and allowed to react for 3 hours. Then, the reaction was stopped,
the content of the reactor was cooled to 30.degree. C., and the
catalyst layer was removed by layer separation. The xylene solution
layer was transferred into a separate neutralization tank, and 500
g of 5% sodium carbonate aqueous solution was added thereto. The
solution was stirred for 20 minutes and then allowed to stand for
20 minutes. The solution was separated clearly into an organic
layer and an aqueous layer which was then separated and removed.
Then, 500 g of water was added to the remaining material, and the
solution was stirred for 20 minutes and allowed to stand for 20
minutes. Thus formed aqueous layer was separated and removed. Thus
separated organic layer was then transferred into a concentration
tank, and distilled under a reduced pressure of 20.about.130 mmHg
at 50.about.100.degree. C. to remove xylene. After removal of the
solvent, 7.1 kg of a light-white solid material was obtained in the
concentration tank. The solid material was analyzed by liquid
chromatography. The result showed 98% purity of
N-cyclohexylmaleimide and 97% yield of N-cyclohexylmaleimide based
on aniline.
Examples 12 to 17
Experiments were conducted under the conditions shown in Table 1
below in the same manner as Example 2. The results of Examples 12
to 17 are shown in Table 1.
TABLE-US-00001 TABLE 1 Addition time (min) Yield Primary Maleic
purity (based on Acid catalyst Solvent Stabilizer amine anhydride
(wt %) aniline) Example o-phosphoric Toluene 2,4-dimethyl-6-t- 5 5
97 94 12 acid butylphenol Example o-phosphoric Toluene
t-butylcatechol 5 5 98 94 13 acid Example o-phosphoric Ethylbenzene
2,4-dimethyl-6-t- 5 5 97 95 14 acid butylphenol Example
o-phosphoric Ethylbenzcne t-butylcatechol 5 5 98 95 15 acid Example
o-phosphoric toluene/xylene(50/ 2,4-dimethy1-6-t- 5 5 97 97 16 acid
50v/v %) butylphenol Example Sulfuric acid Xylene 2,4-dimethyl-6-t-
5 5 95 95 17 butylphenol
Example 18
Into a 300-ml reactor equipped with a thermometer, a cooler having
a water separator attached thereto, and a stirrer, 88 g of a 1:1
mixed solvent of xylene and toluene was added. Then, 6.4 g of
PEG-4000 as a catalyst binder was added, and 8 g (69.4 mmol) of 85%
o-phosphoric acid was added and refluxed while stirring to remove
water therefrom.
Then, 1.2 g (6.54 mmol) of zinc acetate and 1 g (4.54 mmol) of BHT
were added. While the reaction solution was stirred, 20 g (214.8
mmol) of aniline was added for 5 minutes to form an amine salt, and
22 g (224.3 mol) of maleic anhydride was added into the reactor for
5 minutes. Then, the temperature of the reactor was increased to
125.degree. C., and the content of the reactor was refluxed. Thus
produced water was azeotropically distilled together with the mixed
solvent, so that it was removed from the reactor through the water
separator. The reaction was performed at the temperature for 3
hours, and then 1.4 g of maleic anhydride was additionally added
and allowed to react for 2 hours. The reaction was stopped, the
content of the reactor was cooled to 30.degree. C., and the
catalyst layer was removed by layer separation. The xylene and
toluene solution layers were transferred into a separate
neutralization tank, and 50 g of 5% sodium carbonate aqueous
solution was added thereto. The solution was stirred for 20 minutes
and then allowed to stand for 20 minutes. The solution was
separated clearly into an organic layer and an aqueous layer which
were then separated and removed. 50 g of water was added to the
organic layer, and the solution was stirred for 20 minutes and
allowed to stand for 20 minutes. Thus formed aqueous layer was
separated and removed. Thus separated organic layer was transferred
into a concentration tank, and distilled under a reduced pressure
of 20.about.130 mmHg at 50.about.100.degree. C. to remove xylene
and toluene. After completion of the solvent, 33.2 g of a
light-yellow solid material was obtained in the concentration tank.
The solid material was analyzed by liquid chromatography. The
result showed 99% purity of N-phenylmaleimide and 90% yield of
N-phenylmaleimide based on aniline. As a byproduct, 1%
2-amino-N-substituted succinimide was observed.
Example 19
The catalyst separated from Example 18 above was used. 1 g of BHT
was added into the reactor, and then 88 g of a 1:1 mixed solvent of
xylene and toluene was added. The temperature of the reactor was
increased to 100.degree. C., and the content of the reactor was
stirred. Then, the PEG layer was melted and mixed with the solvent.
Here, 20 g of aniline was added for 5 minutes to form an amine
salt. The reaction temperature was lowered to 50.degree. C., and 22
g of maleic anhydride was added for 5 minutes. Then, the
temperature of the reactor was increased to 125.degree. C., and the
content of the reactor was refluxed. Thus produced water was
azeotropically distilled together with the mixed solvent, so that
it was removed from the reactor through the water separator. The
reaction was performed at the temperature for 3 hours, and then 1.4
g of maleic anhydride was additionally added and allowed to react
for 2 hours. The reaction was stopped, the content of the reactor
was cooled to 30.degree. C., and the catalyst layer was removed by
layer separation. The xylene and toluene solution layers were
transferred into a separate neutralization tank, and 50 g of 5%,
sodium carbonate aqueous solution was added thereto. The solution
was stirred for 20 minutes and then allowed to stand for 20
minutes. The solution was separated clearly into an organic layer
and an aqueous layer which was then separated and removed. 50 g of
water was added to the organic layer, and the solution was stirred
for 20 minutes and allowed to stand for 20 minutes. Thus formed
aqueous layer was separated and removed. Thus separated organic
layer was transferred into a concentration tank, and distilled
under a reduced pressure of 20.about.130 mmHg at
50.about.100.degree. C. to remove xylene and toluene. After
completion of the solvent, 34.6 g of a light-yellow solid material
was obtained in the concentration tank. The solid material was
analyzed by liquid chromatography. The result showed 99% purity of
N-phenylmaleimide and 94% yield of N-phenylmaleimide based on
aniline. As a byproduct, 3% 2-amino-N-substituted succinimide was
observed.
Example 20
This Example was conducted in the same manner as Example 18, except
that PPG-2000 was used in place of PEG-4000 as the catalyst binder.
As a result, 32.1 g of a light-yellow solid material was obtained
in the concentration tank. The solid material was analyzed by
liquid chromatography. The result showed 98% purity of
N-phenylmaleimide and 88% yield of N-phenylmaleimide based on
aniline. As byproducts, 1.2% 2-amino-N-substituted succinimide was
observed, and a small amount of unknown byproducts were
additionally observed.
Example 21
Experiment was conducted in the same manner as Example 19, except
that the catalyst separated from Example 20 was used. As a result,
33.7 g of a yellow solid material was obtained in the concentration
tank. The solid material was analyzed by liquid chromatography. The
result showed 98% purity of N-phenylmaleimide and 93% yield of
N-phenylmaleimide based on aniline. As byproducts, 1.2%
2-amino-N-substituted succinimide was observed, and a small amount
of unknown byproducts were additionally observed.
Comparative Example 1
Into a 100-L reactor equipped with a thermometer, a cooler having a
water separator attached thereto, and a stirrer, 20 kg of xylene
was added. Then, 2 kg of silica gel as a carrier was added, after
which 2 kg (17.3 mol) of o-phosphoric acid was added. Then, 30 g
(0.19 mol) of zinc acetate and 30 g (0.14 mol) of
2,4-dimethyl-6-t-butylphenol were added. Into a separate 100-L
reactor, 20 kg of xylene was added and then 4.6 kg (47.3 mol) of
maleic anhydride was added for 5 minutes, and then the temperature
of the reactor was adjusted to 80.degree. C. and 4 kg (43.0 mol) of
aniline was added dropwise to the reactor over 30 minutes. Thus
produced N-phenylmaleamic acid was transferred into the reactor in
which the catalyst had been put. Then, while keeping the
temperature of the reactor at 140.degree. C., thus produced water
was azeotropically distilled together with the xylene to be removed
from the reactor through the water separator. The reaction was
performed at the temperature for 6 hours, and then the reaction was
stopped, the content of the reactor was cooled to 30.degree. C.,
and the catalyst layer was removed by layer separation. The xylene
solution layer was transferred into a separate neutralization tank,
and 500 g of 5% sodium carbonate aqueous solution was added
thereto. The solution was stirred for 20 minutes and then allowed
to stand for 20 minutes. The solution was separated clearly into an
organic layer and an aqueous layer which was then separated and
removed. Then, 500 g of water was added to the remaining material,
and the solution was stirred for 20 minutes and allowed to stand
for 20 minutes. Thus formed aqueous layer was separated and
removed. Then thus separated organic layer was transferred into a
concentration tank, and distilled under a reduced pressure of
20.about.130 mmHg at 50.about.100.degree. C. to remove xylene.
After removal of the solvent, 7.0 kg of a light-yellow solid
material was obtained in the concentration tank. The solid material
was analyzed by liquid chromatography. The result showed 96% purity
of N-phenylmaleimide and 93% yield of N-phenylmaleimide based on
aniline.
* * * * *